text:
At what exact point in time should we be giving the 10 minutes to diversion call to ATC?
I wanted to get some clear information if it’s available as to which exact point should the 10 mins to diversion call be given to ATC with respect to our FOB. The way I have been doing it currently on the A320 is by looking at the FUEL PRED page and when that shows a time value equivalent to 10 mins I give the call to ATC. But this is not a very reliable way to do it while in a HOLD. As the FMGC only updates the extra fuel and time value after crossing the waypoint/PPOS/pseudo waypoint at which the hold has been inserted.
This 10 mins to diversion call is mainly given while flying in India to let ATC know that we only have 10 mins worth of extra fuel left for holding beyond which a diversion will have to be initiated to our filed destination alternate.
Is there any precise way to calculate when we will exactly be at 10 mins?

It would be useful if you could explain where you have heard of the "10 mins to diversion call" and what it means. I for one have never heard that term before, and would not know how to respond if a pilot made that call to me

@expeditedescent the 10 mins to diversion call is a call we have to give ATC while flying in India that our current fuel on board will only warrant us to hold for 10 more minutes after 10 minutes we will commence a diversion to our destination alternate.

I assume your OFP contains the amount of fuel (in kilos) required to reach your alternate + minimum fuel at alternate. And you have your current fuel flow visible right in front of you. So just calculate, with your current fuel flow, how many minutes you have until you only have minimum alternate fuel

That sounds like the answer to me...

What part of the FUEL PRED page are you looking at, EXTRA/TIME? And is this a company specific requirement?

(I just came up with this, so it may not be the official solution - but it should be fairly simple this way)
You first need to know the fuel you need for the diversion with all safety requirements included. This is computed like normal using the MCDU, EFB, etc.. I'll call this your "bingo" fuel. You just need to add the fuel required a 10 minute period for your current flight situation. Once your FOB on the upper ECAM reaches that final result, call ATC.
The easiest way to compute the fuel required for the next 10 minutes is with the fuel flow indication.
On the engine display you have the fuel flow indication, which should be nearly constant during a hold at constant speed and constant altitude.

Add all fuel flow values together
Round up to the nearest 20 kg/hr or so to be safe
Then divide the total fuel flow by 6 (10 min = 1/6 of an hour) to give you fuel required for a 10 minute hold at the current conditions.

Example:
Let's say each of the two engines shows a fuel flow of 1000 kg/hr. Add together to get 2000. Then divide 2000 kg/hr by 6 to get roughly 340 kg fuel consumption for the next 10 minutes. Add this to your bingo fuel.
( 1000 + 1000 ) / 6 = 333 -> 340 ... (+ bingo fuel)
Quicker Alternative:
You could also take the higher of the two engine fuel flow values and divide by 3. Then round up:
1000 kg/hr divided by 3 = 333 kg -> 340 ... (+ bingo fuel)
Note: This works the same if you have fuel flow in pound per hour. The result will be in pounds of fuel required for 10 minutes.

Yes what you ask is definitely possible.
You need to do the following:
Flight Plan: Ensure the flight plan accurately reflects what you expect to do. So you should have a STAR and an approach to the runway in use. Presumably the hold will be on the arrival in use. If it’s not then enter the hold, followed by a discontinuity in the flight plan (enter any waypoint and then delete it) and ensure the routing after the discontinuity reflects what you expect to do. The FPLN should look like this:
HOLD

ILS 22
Alternate: at the bottom of the FPLN will be your alternate. Make sure it has the routing you expect as per your company-issued flight plan, including the arrival and approach to landing runway. Input the average wind component (also shown on the flight plan). Now select your DESTINATION and input a SID that will join up with your intended routing to the ALTERNATE. Remove any discontinuity in the flight plan. Use the PLAN view on the ND which should show what you expect to be an accurate routing from your destination to the alternate.
FUEL PRED page: the fuel for your alternate should now be accurate as you have input your expected route to your alternate together with the wind component. Also ensure the final reserve is entered as per your flight plan.
The time remaining will now show how long is left until you have ALTN + FINAL RES fuel remaining. You’ll be able to work out how long is left until you have 10 mins to diversion time.
Note: the above is only accurate if you input the routing you can reasonably expect to follow.
Bonus tip: for example, if your alternate is north of your destination it may make sense to request a hold to the north of your destination - you’ll be closer to your alternate if you do decide to divert.

I think it would be mostly your discretion on when you decide to divert. I don't really get your question, but I think what you mean is at what amount of fuel should you request a diversion and notify ATC. For this, it depends on the plane model, weather condition, and
much more.
For this example, let's say we're in a 737 approaching Toronto Pearson. We've just previously had two go arounds, and we'realmost on emergency fuel, with 40 minutes of fuel left. If the weather is clear, and you feel comfortable with the approach, you should probably notify ATC, but there is no reason to divert. On the other hand, if the weather is not clear and/or you don't feel comfortable with the approach, you can divert to another airport that you feel comfortable with or the weather is better there. , and if the weather's good, you can simply just declare an emergency and change runways.
If you divert, you should probably go to an airport that 1. is close to your current location (15 minutes away at tops) 2. has good weather and an easy approach, 3. meets your aircraft requirements. If you were at YYZ, the airports that you could divert to include Hamilton, Downsview, and if you've got enough fuel, you can try crossing the lake for Buffalo or Niagra. And if all 3 of these options are not able, you'll have to perform a ditching in the lake.
And as for the ten minute diversion call, it simply means when you have 10 minutes of fuel remaining + the emergency fuel. If you're at this stage, you MUST declare an emergency and divert if the weather or approach is not showing mercy.
I know this was a very complicated and long answer, but since we're all in quarantine, I figured we could all use up some more time. Hope I successfully answered your question, and I'm sorry no one else did.

I used a 737, but it's basically the Boeing version of the A320, so I think you should be fine with that.


text:
Why is the NAV ADR 1 ECAM caution a NO GO as per the MEL on the A320?
There isn't much more I can post about the question but in the MEL out of the 3 ADRs if ADR 1 fails on ground the MEL doesn't allow for a dispatch.

Does Airbus, and/or the airlines that fly them, not provide adequate technical support for these sort of questions?  I'm just curious, because this site seems to have a disproportionate number of very specific and detailed A320 questions.  If I had a real need to know I would always take it up through proper channels before I would trust a stranger on the internet.  Just a random observation FWIW...

Well, I'm not an A320 pilot or technician, therefore, I'll leave this as a comment and not an official answer. I've done a fair amount of study of the A320 as it was the subject of a research project I did for a technical aeronautics course back in college. I know that ADR1 is specifically tied to the ground proximity warning system and that a fault will result in loss of predictive functions of the GPWS and GPWS TERR FAULT light will come on. Because of this, the GPWS TERR pb-sw should be switched OFF. This can present an undue hazard for departure if the issue is discovered pre-flight.

Closely related: https://aviation.stackexchange.com/questions/77353/why-does-an-adiru-1-failure-disable-all-functions-of-the-a330-340-s-gpws-even

@AaronHolmes I think you are so close I would definitely put that as an answer, as inop GPWS is a no go.

@Jpe61 Actually the GPWS can be deferred under MEL for 10 days I believe. So, it is not the reason to keep the ADR 1 operative. Yes, most regulators would not allow operations without GPWS but it is not a critical system for a flight. ADR 1 needs to be there simply for the emergency electrical configuration.

Oh, I stand corrected, thanks @AnasMaaz

It is to prepare the aircraft for a possible Emergency electrical configuration. I hope you are aware of the fact that in an A320, if the AC BUS 1 and AC BUS 2 were to fail in flight for some reason, the RAT (Ram air turbine) extends which in turn powers an emergency electrical generator. When the aircraft is in emergency electrical configuration, only the very essential systems are powered and the others are shed. Some of the systems that are shed include the ADR 2 and ADR 3, leaving only the ADR 1 functional. The ADR 1 will continue to supply air data to captain's PFD. In this situation, the first officer's displays goes blank and the captain assumes the flying duties, if the first officer was the flying pilot when the failure occurred.

If the aircraft is dispatched with ADR 1 deferred, and if it undergoes an emergency electrical configuration, as soon as the ADR 2 and ADR 3 are shed, all the flight displays will go off, including the captain's side instruments which are supplied by the ADR 1. Then you will have to rely on standby instruments to fly which would not be the most ideal condition to be in an already crippled aircraft. Remember, this configuration will force the aircraft into alternate law. Both auto pilots, autothrust and even the flight directors would not be available.

I would assume this to be the better answer.  Look in the MEL and see if one can dispatch with an inoperative EGPWS.  If so, the other answer may not be correct.  I am not a A320 driver.

You can defer the GPWS. But of course you cannot operate aircraft without it in many countries. But it is not the reason for ADR 1. The GPWS is not system critical.

Well, I'm not an A320 pilot or technician, however, I've done a fair amount of study of the A320 as it was the subject of a research project I did for a technical aeronautics course back in college.
The ADR1 is specifically tied to the ground proximity warning system and a fault will result in loss of predictive functions of the GPWS. This is why the GPWS TERR FAULT light will come on after an ADR1 fault. Because of this, the GPWS TERR pb-sw must be switched OFF. This presents an undue hazard for departure if the issue is discovered pre-flight.

This is possibly the correct answer, as I asked a friend who flies A320 and his reply was nav adr 1 drives all the captains panels. so if that is lost the pic can't fly. however it also drives the egpws and a few other things

@Raffles ADR 3 can drive either the Capt or FO displays in place of ADR 1 (Capt) or ADR 2 (FO).  But ADR 1 is the only one connected to the TAWS. Air data is necessary for GPWS Modes 1 (excessive rate of descent) and 3 (alt loss after takeoff). If ADR 1 has a fault and is putting out erroneous but unflagged data, it could result in hazardously misleading information (HMI) from the TAWS. It's interesting to note that it is acceptable in the MEL to dispatch with TAWS inop if "alternate procedures are in place", but the OP is correct in that ADR 1 is always required for dispatch.

@Gerry your exactly right my whole confusion arose because with a GPWS FAULT ECAM the MEL permits dispatch which arose my suspicion that something larger is at hand

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

sort: votes


text:
Why do we have to perform a normal APU shutdown if a fuel spillage occurs?
I was reading in the limitations chapter of the A320 which stated that if a fuel spillage occurs we have to perform a normal APU shutdown what is the reason behind this?

My presumption would be because the apu intake is on the bottom of the aircraft. You would not want fuel fumes sucked into it

Are you asking primarily about why the APU would need to be shut down, or are you asking about why to not perform an abnormal APU shutdown (whatever exactly that would mean)?

@MichaelKjörling my question is simply pertaining to the reasoning behind it as the earlier procedure didn't require us to shut it down. What is the reason behind doing it now.?

I would reason that any source of ignition,such as an APU or vehicle could ignite the spill causing a fire.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
How does the automatic battery cut off logic prevent complete battery discharge on ground in the A320?
I was reading in the electrical systems of the a320 FCOM and in one of the notes it stated that the batteries have an automatic cutoff logic which prevents them from getting completely discharged when on the ground. (Parking)
But how does this logic exactly work? As the batteries are permanently connected to the hot bus in which they will continue to discharge

Not an expert but some kinds of batteries cannot be completely discharged without affecting its life cycle and can even require a replacement instead of a inexpensive recharge. Of course in flight use is critical and thus must be allowed to be drained to the last bit

@Jai, are you looking for a description of the logic (parameters etc.), or a description of how this logic actually (mechanically/electronically) prevents battery drainage?

@Jpe61 I'm looking for a description of how the logic prevents battery drainage specifically when the aircraft is parked on ground.

@Jai selectstriker2 has in his answer described the conditions required for cut-off, and the method used (automatic contactors), how specific an answer do you want?

@Jpe61 the same answer is also available in the FCOM. I kindly request you to read the description I have put.  How does the system prevent complete discharge of the batteries when the aircraft has been parked on the ground. Since number one the battery contactors are now open when on the ground preventing charge and secondly the batteries are permanently connected to the hot bus which will cause them to discharge. So how does this system prevent complete discharge? That's my question

I imagine the system doesn't prevent anything on the HOT BUS from completely discharging the battery. The pilot would use switches to disconnect each piece of equipment on the hot bus when parking the aircraft.

@selectstriker2 your answer is absolutely correct as per the FCOM. But I'm trying to find out more details as to how is this prevented.

@Jai I think that besides the automatic battery contactor logic, nothing prevents equipment on the HOT BUS from discharging the battery all the way. I'm not sure what else you think there is.

According to this page: http://theflyingengineer.com/projects/airbus-tech/electrical/

A Battery Automatic cut-off logic prevents the batteries from discharging completely when the aircraft is on the groung [sic] (Parking).
Automatic battery contactors open when :

The a/c is on the gorund [sic].
The BAT P/b s/w’s are at AUTO
The main power supply (EXT PWR+GEN) is cut off
Battery Voltage is low.

Nothing should automatically disconnect the batteries from the corresponding HOT BUS, so if something is left on the HOT BUS it would continue to drain the battery.

The battery automatic cut off only works when the batteries are left on AUTO. When the battery voltage is low, the battery contactors automatically open, which cuts off power from battery bus and the DC essential bus which preserves the battery charge. It is there for a situation where someone forgets to turn off the batteries during an aircraft securing.

Battery contactors.
However, the hot buses remain powered. So, the logic does not entirely prevent the batteries from discharging. The two voltmeters for the batteries on the overhead panel are actually connected to the hot bus and they keep showing the battery voltage even with the batteries off. And this can slowly discharge the batteries. That is why, it is asked in the FCOM to check if the batteries have a minimum Voltage of 25.5 V, if the aircraft was parked unpowered for more than 6 hours. And if the Voltage is below the limit you need to connect the external and charge them for 20 minutes.
When the aircraft has to be parked for a long period of time, the batteries have to be physically disconnected from the aircraft. According to our engineers, they take the batteries off, if the aircraft has to be parked for more than two days.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
What are the benefits of using thick trailing edge flaps?
I had been reading in numerous articles (see this answer and this one) that there are advantages of using thick trailing edge flaps. In these articles it kept on coming up that Airbus uses thick trailing edge flaps also for certain reasons but I couldn't understand them. Could someone please explain?
My main question is about the aerodynamic aspect: Why do the flaps have to be made thicker?

@ymb1 sorry about that wasn't my intention. Added the other link to.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
How does keeping the parking brake applied when brake temperatures are high contribute to the dragging brake phenomenon?
While going through a presentation on the Airbus WIN application with regard to cost saving practises. It was told with regard to brake life. If the parking brake was applied when the brake temperatures were still high that it can contribute to the dragging brake phenomenon.
Could someone help explain how does this happen ?

From Airbus:

Why is it not recommended to leave the parking brake ON with hot
  brakes?
The SOP recommends to set the parking brake brake back to OFF once the
  chocks are in place when the brakes are hot (refer to FCOM for
  temperature values). This is to prevent transmitting heat to the brake
  pistons potentially causing seal degradation, hydraulic fluid
  overheating and generation of a black aggregate, that can reduce the
  piston running clearance and then lead to brake dragging.

(bolded for emphasis)


text:
Why do we have to perform a full ADIRS alignment between latitudes of 2 degrees North and South on the A320 family?
In the latest FCOM revision under the preliminary cockpit preperation normal procedures chapter ADIRS alignment has been added. However most of the conditions remain the same except for a new line which has been added wherein a full ADIRS alignment has to be performed at airports where the latitude is within 2 degrees North and South.
Could anyone explain with a reference why Airbus has decided to add this ?
As per my company FCOM this is only applicable to certain MSNs (mainly our newest A320-251N's)

@ymb1 nothing has been attached as a note as this got added in Jan 2021.

It's an interesting question, but I doubt someone here will be able to answer it (unless someone from Airbus posts an answer). Can you ask your chief pilot about it? They can probably talk to Airbus directly and will likely get an answer...

This may be related to the fact that near equator the error in coordinates estimation has a larger geographical distance error than the same coordinate error near the poles.

When I look for info about this on the web I see that people interchangeably use high latitude with low latitude numbers, as in high when approaching the north or south pole. This makes no sense, as the poles are 0 degrees latitude. So what is this note referring to? 2 degrees from the poles or 2 degrees from the equator? If they are referring to 2 degrees from the poles, it's likely because it is almost impossible to do a fast IRS alignment that close to the poles. ??

@JuanJimenez, 0° is the equator, poles are 90° (+/- or N/S), always.

@JanHudec I was not asking you about that, I am simply pointing out the fact that some people use the numbers incorrectly.

@JuanJimenez When talking about geographical coordinates, a latitude of 0° is always the equator, I've never seen anyone using a different convention. Maybe you have seen people using spherical coordinates, where $\theta=0$ is pointing along the z-axis (North pole) and $\theta=\pi/2$ is pointing in the x-y-plane (equator)?

@Bianfable "I've never seen anyone using a different convention." I have, threw me for a loop.

I checked with Honeywell, the manufacturer of that IRS system. They told me that they have no clue why Airbus put that in there, as they have no such requirement in their operating handbook. They referred me back to Airbus to ask the question, but I have no contacts at Airbus.

@JuanJimenez that’s very strange and adds further doubt.

.Alright everyone the answer I have posted is as received by my company on raising it with Airbus. Although I don't understand whatsoever how is there excess drift specifically at these co ordinates. Any further inputs to clarify will be much appreciated.

SOP is modified to introduce a new condition to perform a complete IRS alignment during cockpit preparation. When departure airport is located between latitudes 2° north and 2° south, a full alignment must be done. This is to avoid excessive drift of Honeywell ADIRU Block III during the subsequent flight.

What is it about being within 2 degrees of the equator that makes excessive drift of the ADIRU a problem?

@WayneConrad unfortunately thats the answer I got when raised it with my company's flight operations department who in turn raised it with Airbus. This was their response.

It seems the answer is, "we made the change because we needed to make the change".


text:
What is the purpose of the pressure relief door fitted on the PW1127G-JM engines of the A320NEO?
Hey guys many times during my exterior walkaround I noticed on the A320NEOs that they have this pressure relief door and our SOP for the exterior walkaround states to check that this door is closed. However I would like to know what is the purpose of this door? As it's not mentioned in the FCOM.

Inside the nacelle cavity of a turbofan engine and in the casing of the engine core, there are different zones or closed compartments used for ventilation/cooling and in the case of the nacelle lip, also for anti-icing (see the first two images below). If a highly-pressurised duct (such as the anti-ice inlet duct shown in the 3rd image) bursts, the pressure builds up to a dangerous level, despite the ventilation exits. To prevent structural damage to these closed compartments, pressure relief doors are installed which are triggered automatically.

Edit: my first answer lacked some details, so I rewrote it.

I've edited my answer. Is it more clear now?

Yes, that is great, thanks very much. I will delete my previous comment (and also this one, later). Cheers.

Is this specific to the PW engine? The door is a thrust reverser pressure relief door as per the FCOM.

Pressure relief doors are definitely not specific to the PW engine. Even, it seems like in other engines, they are also used for the thrust reverser compartment (zone 3). Check out this discussion: https://www.pprune.org/archive/index.php/t-403785.html


text:
What's the difference between flight level and pressure altitude?
When should we say flight level and when should we say pressure altitude?
I know they both set QNE 1013.25, but there is a difference between them.
Anyone know?

Flight levels are pressure altitudes.

Flight Level specifically refers to Pressure Altitude in 100 foot increments within the Standard Pressure Region, which in North America starts at 18000 ft and above, and at various lower altitudes elsewhere.
If you are in the Altimeter Setting Region where you set local barometric pressure to get indicated altitude, you normally use indicated altitude and could state the pressure altitude if asked, but you wouldn't use the term Flight Level.

Below are three answers: When should we say which, and what is the "difference" between the two terms.

Let's start with Pressure Altitude. There are lots of more-complex answers in various publications about what pressure altitude is, and many of them are already discussed on this site.  A "short and sweet" answer is: Pressure Altitude is simply the "height above a standard reference point at an agreed-upon air pressure measurement".
We use sea level as the reference point, and 1013.25 hectopascals (hPa) as the agreed-upon "standard pressure setting".  This atmospheric pressure is the equivalent of  1013.25 millibars, 29.92 inches of mercury, and 14.696 PSI.
Pressure altitude is useful for many things, but one of the most important to aviation is that almost all aircraft performance charts are based on pressure altitude. To a pilot making calculations, such as how much runway length will be needed to land or take off, the pressure altitude is one component of that formula.
For example: we know that Denver International Airport is at an elevation of 5430 feet above sea level.  If there is a low pressure system in this area of about 970mb, then the Pressure Altitude for DIA will be at about 6500'.  When a high pressure system moves in a few days later, the Pressure Altitude could drop down to around 4500 feet. These different pressure altitudes at the same location could prevent some aircraft operations that might normally be doable.
Summed up: Pressure Altitude is how high above (or sometimes below) sea level the current air pressure "feels", and can have a significant impact on aircraft performance.

Q: When should we say Pressure Altitude?
A: Whenever we need to know what the relative height above sea level is for a given location, so that performance calculations can be made.

Now let's move on to Flight Levels.  Flight Levels (FL) are "officially designated" pressure altitudes at or above the official transition altitude (TA). These TA and FL designations are different by country, or even within different terminal areas of the same country. As you noted in your question, a Flight Level is determined by setting your altimeter to QNE and then reading the value on the altimeter.  But this reading is only a "Flight Level" when the aircraft is above the TA.
Within the US and Canada, the TA is at 18,000 feet of altitude. If the regional QNH is 1013.25 hPa, then Flight Level One-Eight-Zero (FL180) will be right at 18,000 feet of altitude. FL200 will be right at 20,000 feet of altitude. However, if there is a low pressure system then FL200 could be all the way down at 18,000 feet.
(note: In this low pressure example, aircraft will not be assigned a flight level of FL180 or even FL190, because it would be unsafe - the aircraft would actually be at about 17,000 feet and below the Transition Altitude and interfering with other, possibly non-controlled, aircraft. Therefore, on this low pressure day, it would be said that "the lowest available Flight Level is FL200".)

Q: When should we say Flight Level?
A: Whenever we are talking about aircraft that are flying above the Transition Altitude, and assigned to a specific pressure altitude.

And finally, your 3rd question:

Q: What is the difference between the two?
A: A flight level is always "an officially-designated pressure altitude". But, any given pressure altitude is not necessarily a flight level, and will be used for purposes other than just determining flight levels.

The pressure altitude can be determined by either of two methods: 1. Setting the barometric scale of the altimeter to 29.92 (1,013.2 mb) and reading the indicated altitude. 2. Applying a correction factor to the indicated altitude according to the reported altimeter setting.
Airliners generally set the barometer to 29.92 when climbing thru 18000 feet and then fly the flight level they are cleared to.
When descending, the barometer is set to the local pressure, updated as needed (every 50-100 miles or so) and fly the assigned altitude (such as "descend and maintain 15000, one five thousand").
Us smaller guys just set to the locally reported barometer setting. (I've only been up to 12500 feet in my plane - and have actually driven higher, 14110 feet, to the top of Pikes Peak in the Rockies.)


text:
What aircraft is this compass from?
I have come into possession of some of my grandfather's things including some aircraft parts that he had. He was a naval pilot who flew single-engine fighters in WW2 and then at some point transitioned to flying helicopters (some sort of Sikorsky) which he piloted in the Korean war. After he retired from the Navy he continued to fly as a civilian contractor for the Air Force until around the 1960s.  It may have come from one of those aircraft but it seems too big to be in the cockpit of a WW2 fighter plane.
Unfortunately at some point the needle(?) fell off the pivot and I would like to try and repair, it but I'm worried about the potential liquid inside - which, if I had to guess, might just be mineral oil.
I have several questions about this compass:

What aircraft is it from?
What is the purpose of the gearing on the back of it?
What liquid is inside it?

The US Army Air Force and Navy compass type D-12 encompasses several models manufactured by  Bendix/Pioneer: 1801, 1826 (yours), 1832 and 1833. The D-12:

Is a direct reading compass, not a fluxgate.

Is aperiodic, there is no dampen harmonic oscillations, the plate settles with a single rotation.

The D-12 was found on several WWII transports and bombers. As you assumed, it wasn't a pilot instrument, but an instrument for the navigator. From this site:

The US Army Air Force Type D-12 Direct Reading Aperiodic Compass was used at the navigators station across many US WWII aircraft, including heavy bombers B-17, B-24, B-29, medium bombers B-25 and B-26, and transports C-46, C-47, and C-54.

Here in a restored C-53, the navigator station is located just behind the pilot, on the left side:

Source.
Answers to your other questions are found in this maintenance documentation from the Royal Canadian Air Force:

The compass fluid is compliant with specifications 3-GP-31 (a retired CGSB standard for refined petroleum free from moisture, acidity, glue, suspended matter or other impurities).

The mechanism at the back is a compensator with movable magnets to cancel magnetic perturbations created by the aircraft.

The documentation provides additional internal details, the recommended disassembling and checking procedures, etc, and this cutaway drawing:

Wonderful! :) ...


text:
Why don't Airbus planes have perfectly smooth front sections?
From time to time I like to watch a planespotting video and I must say that one tiny detail bothers me a slight bit.
Look at this Boeing plane:

And at this Airbus:

In particular, examine the section directly above the windows, in the middle. Why is it so smooth with most Boeing planes, and why does it have this crease in many Airbus planes (including the A380, but I think excluding the A350)?
It reminds me of playing with 3D modelling software long ago. I found it difficult to get these curves perfectly smooth - but surely Airbus designers have more skill than I do!  So what is the real reason?
Credit: I have taken these images from a YouTube video.

Do you maybe have the photos backwards?

@MichaelHall Backwards as in? looks correct to me...

Very much related: Why, until recently, were smooth nose sections not popular?

It is not about Boeing versus Airbus, but rather about old versus new.
Your representative image for Airbus is an A320, whose technological competitor by Boeing is the 777. Juxtaposing the two, we find that the feature in question is present on both aircraft:

 Image Sources: Boeing 777 versus Airbus A320
Likewise, the technological competitor of the 787 is the A350 (and maybe the A220) - all three of which have a smooth nose section.

 Image Sources: Airbus A350, Boeing 787 and Airbus A220
Camille Goudeseune's answer explains correctly the reason for this feature on older aircraft.

The pinched-nose airplane has its (flat) frontmost windshield panels almost touching and raked back, which forces the vertical crease.
The corresponding panels on the other airplane are farther apart, nearly coplanar, and may be curved as well, so the space between them can have a larger radius of curvature.
The reasons behind those design choices quickly get complicated.  But for a start, flat windows are cheaper to design and build and have less optical distortion.  G3 curvature will be pretty far down on the list, compared to cars and kitchen appliances.

Excellent reference to G curvature

I think you're comparing a 787 in to top to an A319 in the bottom.
The 787 is unusually smooth in that area.  It is a composite airframe, which allows some additional freedom to use curvature.  You might want to compare to a broader selection of aircraft.
I am not positive, but I think they may have used curved glass on the 787 -- but only a simple curve (one direction).  However, the A319 you show clearly uses flat glass.

"It is a composite airframe, which allows some additional freedom to use curvature" -- This is true, but there are plenty of aircraft constructed with traditional materials that do have a smooth nose section. See: C919 and A220

IMO it's not clear that composites are "easier to curve".  Completely free-form 3D surfaces are really really hard (in terms of everything from design to simulation to indeed manufacture).  I'm not sure it's particularly harder, the literal manufacturing, with traditional materials V. composites.  I dunno.

Sheet metal can be easily bent in simple curves without stretching or shrinking the metal.  In order to make compound curves, you must deform the metal.  This isn't a huge obstacle on an industrial scale where you can make appropriate tooling.  So for these aircraft it probably isn't very important.  For homebuilt experimental aircraft, forming metal to compound curves by hand for one-off parts is very difficult.  It is much easier to carve a mold and lay up composites over that mold.

@RobMcDonald more precisely, forming aircraft-suitable metals to compound curves by hand is difficult. Doing it in copper, brass or certain types of steel is actually fairly straightforward, but those would be to weak and/or heavy for a plane.

Building upon this question and the relevant answers, it might have been not only a technical reason (aerodynamics or bird strike resistance) but also a simpler aesthetic/corporate reason in order to help distinguish an Airbus back in the '70s when Airbus was born and started to compete against Boeing, McDonnell Douglas and Lockheed.

Huh! Could well be.


text:
Why might using flaps trip the breaker on a Cessna 172G?
Why does the breaker keep tripping when I try to use the flaps in my 1965 Cessna 172G? It’s a 15 amp breaker.  After I reset the breaker, the flaps will go up but then the breaker trips when attempting to lower the flaps.

Something is wrong with your flaps, the wiring leading to them, or the breaker itself. The breaker is tripping to keep your plane from starting on fire. Stop resetting it and have a mechanic look at it.

Very well said!

Thanks will do.  I forgot to mention that after I reset the breaker the flaps will go up but then the breaker trips when attempting to lower the flaps.

Electricity can be very moody if you have a fault somewhere. Any! movement of the plain, even you shifting your position on the seat can shift cables and affect a short circuit, cause the cables move a little and then there is no shortcut anymore, until the next movement. Also these kind of shortcuts are very dangerous, cause they can create an electric arc, which really can set you plane on fire.
It's also possible that the flaps are clogged and move with more resistance than they should, especially overcoming initial static friction (in any system) takes a lot of force and hence current.

We used to say that a tripped circuit breaker is an electrical fire "push-to-start" button.

Thanks everybody confirming the plane has been grounded since first experiencing tripped breaker.

Question: does the breaker open immediately when you command a flap setting, or is it more intermittent ie it occasionally trips when commanding a flap setting?  An immediate and instantaneous trip typically indicates a short circuit either in the flap drive motor, the control switch unit or the wiring.  Intermittent tripping of the breaker might indicate problems with the flap drive motor i.e. damage to the windings, etc.  Either way, the flap system is a secondary flight control and must be functional in order to fly the airplane safely. Therefore cease operation of that aircraft until the flap system can be inspected and repaired by qualified mechanic.

Thank you for this.  The breaker trips immediately.  Trying now to get a mechanic to return my calls.  If anybody can refer a mechanic in or near Byron, CA please send me their contact info. Thx.


text:
What would define a thunderstorm that you would stay 20 miles away from?
In summer time, we get pop up cumulonimbus clouds that often develop into thunderstorms. So is there a defined point at which it would be considered a thunderstorm to stay 20 miles away from? Is it the “thunder” aspect (I.e. lightning)? Or is it a personal judgement call? Or is there a clearly defined definition I’ve missed?

The definition I would use is "when it reaches the mature stage".  Because before that it is a cloud.  You are probably familiar, but here's a good link:  https://www.aviator.zone/pireps/2021/1/14/3-stages-of-a-thunderstorm  And even at the mature stage, 20 miles on the upwind side cruising at medium altitude is pretty conservative.  You are more vulnerable low and slow during approach.

Well, you won't get a ticket if you get too close, but please remember thunderstorms can produce very violent winds, and the cloud is produced by the updraft.
Sinking air and turbulence may be present in the clear air around it.
Although lightning can strike "out of the blue" many miles from a thunderstorm, it is the unpredictable wind conditions in and near the storm that pose the greatest risks to aviators.
Also, thunderstorms can rapidly develop, and radar information even 20 minutes old may be inaccurate.
Any area of instability should be avoided, meaning don't fly there that day unless you absolutely have to.
The FAA Advisory Circular AC-0024 C section 10 a. Thunderstorm Avoidance, line 14 states the 20 mile limit is for storms of a "severe" nature or giving an "intense" radar echo.  Line 15 also recommends avoidance of areas where thunderstorm coverage is 6/10.

I appreciate your answer, I’m gleaning that your interpretation falls under the “personal judgement” side of things. I’m just curious of whether or not the FAA has laid out a clear definition. I’m guessing not, as they often leave certain terminology vague seemingly on purpose.

I would also say that nearly every day in the summer at my location has pop ups at some point in the day, so it’s unavoidable to continue flight training over the summer and to completely avoid areas of instability. Unless you just mean avoid all cumulonimbus development to which I completely agree with. The question is, by how far should they be avoided.

@RattMuscle I guess this is why checking the METARS is so important.  20 miles would be more towards a developed or severe storm, and, indeed, thermals underneath fair weather cumulus are gliders friends.  It's the forecast that's important, especially if there is an approaching front.

This is a good answer to “what are the hazards associated with flying too close to a thunderstorm?”  Maybe the OP should change their question?

It’s a good answer, but I was more interested in finding out if there was an FAA definition for what defines a thunderstorm that would require significant avoidance.

I've come across a rule of thumb that says to stay as many NM away from a storm as its tops in '000s of feet.  So 20NM would be a minimum distance for a  storm that tops out at FL200.   For a really severe storm topping out at say FL450, give it a 45NM berth. This reflects the horizontal distance that hazards like hail and turbulence can be found from a big storm, especially on the downwind side.


text:
How do bleedless passenger airliners keep cabin air breathable?
When you web-search an answer for how airliners maintain cabin air breathability, the typical answer you get is that bleed air is the key: new air comes in from the outside and gets mixed with old air.
But these days, some airliners are bleedless, such as Boeing's 787.
So, what maintains air breathability/quality in the cabin? Do they use oxygen tanks and some kind of CO₂ capture mechanism? What about other kinds of air treatment, e.g. for other gases, organic material etc?

This is an airplane, not a spaceship. There's still a lot of oxygen outside the cabin that you can just pump in.

@user3528438 Well, it's not "just" pump in. It is a pressurized body.

Bleed-air must be cooled with cold air from the outside. So there are already cold air (ram air) inlets used by the heat exchangers with bleed ECS, even if this air doesn't reach the pressure vessel. Here is a traditional pack with its prominent ram air inlet. (Source).

Here (pdf) you'll find a nice Boeing document about the bleedless system used on the B787.

Bleedless aircraft still get air from outside. They just have dedicated compressors to compress outside air for cabin use, rather than relying on bleed air from the engines.
The air compressors have outside air ducted directly to their inputs and compress the air to the proper cabin pressure. It works identically to bleed air otherwise- fresh outside air is brought in through the compressors and stale inside air leaks out or flows out through dedicated outflow valves.

This system along with thermal electric anti-icing forced Boeing to go with very large L-ion batteries, leading to the fires, and the need to build a L-ion-fire-proof enclosure after grounding the fleet. On the C-series/A-220, there was considerable thought given to using them to save weight, there being significant electrical services (although not like the 787), but they, perhaps wisely, decided to stick with nicads.

@einsupportsModeratorStrike See the image in this answer.

@Bianfable: Is that also used for exhausting air?

@einsupportsModeratorStrike No, the ram air has specific ram air outlets a bit further aft. The cabin air is exhausted through the outflow valve(s). They are typically located towards the aft of the cabin (sometimes there is one further forwards, but not sure for the 787).

@JohnK: "This system along with thermal electric anti-icing forced Boeing to go with very large L-ion batteries" that's the concept of MEA, more electric aircraft, the generators power also increased from 600 kVA (A380) to 1000 kVA (B787). "leading to the fires", Airbus continued with Ni-Cd units for the A350 after Boeing's problems, but that's only temporary. More in Aircraft batteries: current trend towards more electric aircraft

Needs a new technology beyond L-ion. Something that doesn't randomly turn into a road flare.  I like aluminum-graphene, if they figure out a cost effective way to mass produce graphene on an industrial scale. To actually power airplanes electrically engine wise, you need to triple energy density. Even there, you are stuck with "full fuel weight' which hampers the ability to trade payload for range, a serious limitation.

@JohnK I wouldn't hold my breath on graphene. The fact is, currently Li-ion is the best technology, thanks to the huge amount of research and refinement that has already gone into it. It can fail of course, but everything can fail. Most cells never turn into road flares. The way to go with something that fails sometimes is not to abolish it (unless a demonstrably better alternative is already available), but to add encapsulation and redundancy and push to reduce the failure rate further (which is also something the battery industry works on intensely).

...Energy density is another matter: indeed Li-ion will probably never be able to power a transatlantic flight. But that's independent of its capability of fiery failures. And it's quite possible that no battery technology will be able to power a jet-like plane across the atlantic for many decades to come, and we need to find entirely different approaches. I hold the most hope for ammonia as fuel.

tl;dr: Through air intake holes using compression.
For example, here they are on the fuselage of a Boeing 787, below the forward edge of the wing:

Bottom intake air gets compressed (and thus heated)
Top intake air is used to cool the compressed air (and is called "ram air"; it never goes into the cabin)
Cooled, compressed air is then released into the cabin (somehow)

Further reading:

This more detailed answer by Bianfable.
This explanatory and somewhat technical document from Boeing about their bleedless system on the 787.


text:
Ferry Permit for aircraft outside the U.S
The aircraft originally had a U. S. airworthiness certificate then was exported to Brazil. It is now being sold to a company in the U. S. for U. S. operations. Can this aircraft be issued an "N" number and Ferry Flight permit for the purpose of returning to the U. S. where an application for U. S. Airworthiness Certificate and permanent registration will be pursued?

Can the owner get a registration, then the ferry permit, and once arriving in the U.S. apply for the standard airworthiness certificate after completing any inspection requirements?

Yes, as long as the aircraft has no outstanding AD's that make no allowance for ferrying the a/c to a location to achieve compliance. If it has AD's that don't mention ferrying to do that is OK, the aircraft cannot be ferried until the AD(s) is(are) complied with.

If the aircraft was taken off the US registry and registered in Brazil, the answer is no. You have to reverse the process to put it back into the US registry, and until it is, you can't ask for a ferry permit from the FAA.
For the benefit of those who may not know the process:

A request is made in Brazil to deregister the aircraft, with a note to send a copy of the deregistration certification to the FAA. The seller needs to request this in Brazil; the buyer cannot make the request, neither can the FAA. Processing of this request can take anywhere from two days to several weeks, particularly if the aircraft is registered to anything other than an individual and/or if there are any registered liens on the aircraft.
The Brazilian government sends a notification to the FAA that the aircraft has been deregistered.
A registration form with either a previously reserved N-Number or by default letting the FAA assign one is sent to the FAA, along with a valid bill of sale. If the bill of sale is from Brazil, it must be notarized by a Brazilian notary and apostilled (certified) at at any public notary office (cartório). If it is in Portuguese, it must be translated by a certified public translator, a list of which may be obtained from the Junta Comercial of any state in Brazil. If you don't do these last two steps the application could be rejected. Better to use the FAA form for the bill of sale.
Once the FAA receives the registration request, it verifies that it has received the deregistration confirmation from Brazil. No registration will be issued until that happens.
A registration certificate is issued and mailed to the person or entity on the registration form.

You can then make arrangements for a ferry permit, but keep in mind that the procedure to request a special flight permit (the official name for a ferry permit) has other requirements, including sending a copy of the current airworthiness certificate, portions of or all of the logbooks, etc.
Also, if the aircraft has any outstanding AD's that have not been complied with, and the AD notice makes no allowance for ferrying the aircraft to a location for the purpose of achieving compliance, the ferry permit will not be issued. You will have to bring the US mechanic to the airplane (or find a local FAA-licensed mechanic, possibly an IA as well depending on the nature of the AD) to take care of it.
Bottom line is talk to your local FSDO first before any money changes hands to avoid any unpleasant surprises. The process above can be applied to an aircraft in any country, just change the references to Brazil.
(If you see an error in this explanation, or something that needs clarification, please add a comment so I can correct it or further clarify it.)


text:
Does a headwind/tailwind affect your rate of climb?
I am still confused whether a head wind or tailwind would affect the rate of climb. Since in a HW/TW condition our a/c is basically still climbing in the same parcel of air, it is just that parcel of air is moving with or against our course hence increasing/decreasing the horizontal distance covered to get to the target height. This means that the time needed to get to the target altitude is not affected at all, but the horizontal distance is.
Yet my friends have been insisting that with a headwind an aircraft would climb faster to the target height, as the headwind helps create more lift by increasing the amount of air passing through the wings.

Consider the extreme case: What happens if you are climbing in a direct headwind where the horizontal component is equal to the ground speed at best climb?

A headwind or tailwind affects your angle of climb. In a headwind you cover less ground for the same gain in altitude, so you're climbing at a higher angle relative to the ground.

Possible duplicate of Does a headwind affect the climb gradient?

This is not a duplicate of the linked question. That one is about the climb gradient, which is different from the rate of climb asked about here. The answers on the linked question explain why.

Your friends may be assuming that you can somehow maintain constant ground speed.  Perhaps you need to emphasise that isn't the case?

To your friends: Does walking to the east or west affect how tired you feel?

Your friends are groundlings who cannot seem to shake the paradigm that an aircraft is somehow connected to the earth, like a kite on a string.  Once airborne the only thing the airplane recognizes is its relationship to the airmass.  That airmass can be stationary relative to the earth, or it can be moving across the earth's surface in the form recognized by observers on the surface as wind.  However, the aircraft does not perceive this as wind.  It is called "wind" because that is the common term for it, and it is a useful reference in terms of its effect on travel over the ground.

A steady (continuous) head wind (or tail wind) will not affect your climb rate, only your climb angle. It means you will reach a specific altitude in the same time interval, but your ground distance will be affected.
A head wind increase (as in a gust) will momentary increase your indicated airspeed, which you can trade for a (momentary) increase of climb rate. Similarly, a tail wind gust will temporarily decrease your indicated airspeed and you might have to pitch the nose down a little, to maintain airspeed and therefore reducing climb rate. These are only transitory effects, until the plane settles back to its original trim speed.

Your climb rate is dependent on your airspeed. If you are doing the same airspeed your rate of climb will be same no matter what the direction of wind is compared to your aircraft.
Just to clarify that climb rate is also dependent on pitch, but the general rule of thumb is that power controls climb and pitch controls speed. In reality you use both, but climb is not dependent on wind speed.

Climb rate will also depend on your pitch angle at a given airspeed!

Sure.  And on engine power output.  And on weight of plane.  Not sure how that comment is relevant to understanding or improving answer.

I assume you don't mean to suggest that pitch attitude somehow depends on orientation with respect to wind

What i was trying to do is dispel the myth that wind direction affects climb rate. We know as pilots that you control climb with throttle and speed with pitch. Obviously it is a combination of the two, but those are the rules of thumb, not how strong the wind is blowing.

My comments were directed at Bianfable's comments not your answer; didn't make that clear.  The answer is fine.


text:
Are high lift wings bad for faster speeds
I notice a trend in many aircraft designs. If the aircraft was designed to go slowly but have shorter takeoffs/landings they use airfoils with a high lift.

However for long endurance flights they use a flatter airfoil that produces less lift.

To my understanding the reason for this is because you never get anything for free. When a wing produces lift, it is trading the forward movement of the plane for vertical movement.
I understand that at higher speeds the high lift wing would fight horizontal movement too much and so they chose the flatter airfoil.
However my question is what if you change the angle of attack for the high lift wing? Pointing the front of the wing downward, thus making its lift more of a forward direction.
Would this somehow still be less efficient than a flatter airfoil or do they just chose the flatter foils for design purposes and structural reasons?

what if you change the angle of attack for the high lift wing? Pointing the front of the wing downward, thus making it's lift more of a forward direction.

The engine of the aircraft creates forward movement.
The wings (and body) of the aircraft absorb some of this forward movement energy to create lift and drag.
If you simply change the angle of attack to have the lift vector pointing into a more forward direction (instead of upward direction only) you still create the drag in proportion to the lift. Therefore if you want to fly high speed it is better to have a wing with less lift resulting in less drag.
On the other hand the lift to drag ratio depends on the angle of attack too. So if you change the angle of attack away from the best ratio angle (in either direction) you get less lift and more drag. Unfortunately the ratio gets worse faster for negative changes (nose down) than for positive changes (nose up).

Every airfoil has a range of lift coefficients where the flow around the wing is most favorable. Airfoils with high camber shift this range to higher lift coefficients. Now the question comes down to: At which lift coefficient will the aircraft operate most efficiently?
The efficiency of transport aircraft is maximized when none of the three parameters payload, range and speed can be changed without reducing the product of the three. As it turns out, wing weight has a big influence on this, especially for large aircraft: A heavier wing will reduce the possible payload. It is better to limit wing span such that the ratio of wing span to chord is between 7 and 10: This will limit the bending moment at the wing root and allow to build the wing lighter. At this aspect ratio, the optimum lift coefficient for best transport performance is around 0.4 to 0.6, a number at which the low camber airfoil will feel right at home.
At such a low lift coefficient, however, the high camber airfoil, on the other hand, will experience a strong suction peak on the lower side of its nose. At high flight Mach numbers, this will lead to locally supersonic flow and a big increase in drag as well as cyclic loads on the wing (buffeting).
Now you could correctly argue that the wing could be much smaller with a high camber airfoil for the same lift. Yes, but the wing needs to adapt to take-off and landing conditions, too, and needs to have enough volume to contain the trip fuel. And for this landing condition the wing of an airliner will even have more camber than your example airfoil:

Typical landing configuration of an airliner wing, from an article by A. M. O. Smith, McDonnell-Douglas, in Journal of Aircraft, Vol 12 No 6, 1975.


text:
Which simulator is appropriate to learn the minimum to land an airliner?
If one has zero flight training, but wants to learn the basics, so that they might be able to land an airbus in a Helios 522 type scenario (or any double pilot incapacitation for that matter), what would be the best simulator to learn on and what specifically would be best to learn (basically how to communicate with ATC and perform an auto-land).
I am fully aware that it takes thousands of hours of training to learn to fly and do not expect to be some sort of pilot after just using a simulator. Basically the premise of the question relates to increasing chances of survivability in-case of such an emergency and there being no other experienced people on-board (even if the increase is only by a few percentage points:)
Edit: Also, if the flight crew were all incapacitated, how would one enter the cockpit?

"Also, if the flight crew were all incapacitated, how would one enter the cockpit?" - I'm not going to claim to know for certain but I'm pretty sure you can't.

Your bigger problem is how to get into the cockpit with the door locked from the inside and two incapacitated pilots. The referenced attendant could get it because he knew the code to get emergency access, you as a passenger do not. The door is incredibly resilient as evidenced by the Germanwings crash when the copilot locked out the pilot.

Do you want an actual approved simulator built by the aircraft manufacturer (which will likely mean a full-motion simulator), or do you want something that runs on your home computer without any extra hardware, or something in between?

Definitely related, not sure if it's a duplicate: How can passengers help in the cockpit in an aviational emergency?

@DanPichelman Not a duplicate, but I agree definitely related. This question would be more about how to prepare yourself for such an eventuality. (I guess the answer to that might be "get a commercial pilot's license and a handful of appropriate type ratings"...)

@MichaelKjörling Hi, Michael, I did mean something I could run at home. The question seems controversial, it has swung from ratings as low as -5 to a +3 at one point and is now back down.

"I am fully aware that it takes thousands of hours..." you're just flat wrong.  An ATP license currently requires 1,500 hours. Until very recently, it only required 250 hours.  In no sense is that "thousands" of hours.

Any potential flight deck access is something that should not and hopefully will not be discussed here.

Although it's phrased differently, this seems close to being a dupe of this question and/or this one

@abelenky Ok, so I just need 250 hours of study to achieve this>?

Under old rules, 250 hours of flight time was the minimum needed for a Commercial License.  That does not count ground-school.  Under current rules, its 1,500 hours of flight time.

@Cloud Please, you have literally no way of knowing who has downvoted your question. Please don't make assumptions.

So it would not be possible, just to learn how to communicate with ATC and have them, have a pilot 'talk you down', step by step?

From another question: As long as one is smart enough to locate the operations manual and contact ATC, landing a modern commercial jet on an airport with the necessary ILS equipment should be a piece of cake thanks to autoland. Even without it, landing a functional aeroplane in good weather on a long runway is not rocket science. It is very easy. The times when pilots really need their experience and earn their salary is in emergency or bad weather. I suspect that even the brightest without experience would not be able to deal with strong crosswind.

A pilot could talk down a novice, step-by-step, in the same sense that Slash from Guns'n'Roses could "talk" a novice guitar player through a solo-shred- step-by-step.

Adding to @abelenky above, I can't help but compare this to trying to talk a novice computer user through diagnosing what's wrong based on detailed error messages. (And that's a situation in which you have basically unlimited time!) The novice user has no idea what's important and what's not, and lacks the experience to make a judgement about importance. Now take such an error message and multiply it by 1,000, and you've got a typical airliner cockpit's complexity. You have literally seconds to identify what's important, relay it, understand the response, and take corrective action. Good luck.

(And even that is assuming that you make the right call about what's important and what's not, so that whoever is on the other end of the radio link won't need to ask for any clarification or additional details. Unlikely, but maybe technically possible with a thorough briefing earlier on the form "ignore any lights or messages that aren't red" and the like...)

I feel this might be a duplicate: https://aviation.stackexchange.com/q/738/1467

The simple answer is: none.
Flying an airliner (never mind the difficulties of getting into a locked cockpit) is not just a matter of wrestling with some controls. And, unfortunately, you would indeed need to be "some sort of pilot" to do that, including "just" being able to "communicate with ATC and perform an auto-land".
Even if you were a qualified pilot of a different aircraft, you'd be staring at a sparkling ocean of "what the hell do these do" buttons, lights, knobs, switches, levers and other controls.
You might as well ask what kind of simulator would prepare you for playing first violin with the Vienna Philharmonic orchestra, or taking charge of a nuclear power station.
They are just not things that can be done without much study and training, without which you literally wouldn't even know what you are looking at.
This is quite sad, because I for one would be quite happy to be known as that person who stepped in and saved the day when the pilot/first violin/nuclear power station chief engineer was suddenly incapacitated.

This answer is so funny, that I just have to accept it - even though Kevin's answer is probably more on-point. It seems that this can be done, if one puts is a few hundred hours of study on a good simulator.

Your chances are none.
I'd like to refer you to this TV episode, where a person with no flying experience at all attempts to land a Boeing 737 with just one month of training:

He spent 20 hours learning to fly a light aircraft, and was allowed to fly solo in that airplane by his instructor
After that he attempted to land a B737 in a professional simulator, and crashed on the first landing attempt even with an instructor pilot sitting next to him in the cockpit
After weeks of training in the professional simulator, his attempted to fly the real aircraft. His first landing attempt failed and the instructor stepped in to save it. His second attempt was successful but was a kind of a hard landing.

Which simulator is appropriate (...)

If even a professional simulator with an instructor pilot to the side fails to teach a young pilot to land a B737, I am convinced that there is no simulator which would let a person "with zero flight training" to land an airliner when all pilots are incapacitated, assuming that you can get through the cockpit door.

That aside, there are products which simulate airliners to great detail on the home flying simulator market. You will have to spend at least hundreds (if not thousands) of hours to study the materials though.

I'm no expert, but isn't comparing a 737 to an airbus a bit unfair? Would an airbus be easier?

Please keep it nice gents

@Cloud Comparing a 737 and an "Airbus" is toatally appropriate in this case. They're not that different that the answer to this question would be any different materially


text:
What is the most fuel-efficient flight profile for a small plane?
If you take a short one hour flight in an A320, the flight will usually climb to around 25 - 30,000ft and then descend into its destination. The actual cruise at 30,000 will often only be a matter of minutes. The reason for this, I understand is it's the most economic (fuel sparing) flight path.
What is the most economical vertical flight path to take when flying a small plane (say a 152 or ultralight) for a flight duration of around an hour?
I recently tried the "A320" approach by climbing to 10,000ft (the flight ceiling) and then switching to idle. But since small planes often don't have a great glide ratio, including the one I used (C42), I believe that flight was less economical than usual, it took a very long time to get up there at a fairly high power setting.

Note: airlines uses (and adapt) a factor to calculate that, which may include too much parameters. Possibly you should restrict: more fuel efficient way, right? (so without taking into account time, wages, etc.)

Similar: How do I determine the best altitude to fly for fuel economy? and for commercial airliner insight: How do pilots decide what their cruising altitude will be?

If you're using Skydemon, it will calculate the best altitude for you for a given flight. You of course need to have it configured with your fuel burn and it needs up to date weather.

Flight ceiling is, pretty much by definition, maximum but not optimal. For example, A320 has a service ceiling (based on a quick search) of ~ 40,000 feet. If the typical 1-hour cruise only for a little bit flight hits 30,000, and in fact most longer flights probably somewhere between 30k and 35k, the logical thing for a small place with a ceiling of 10k would be optimum somewhere below that - e.g., perhaps 5k or 7k or similar.

The fuel burn on a jet is so awful at low altitude it's worth it to get as high as possible as soon as possible even for a short leg like that. On a propeller lightplane there's a difference but it's a lot more subtle. In any case, if you're paying for the airplane, wet, on a Hobbs meter, your economic incentive is to get there as soon as you possibly can and fuel burn doesn't come into it, so the most efficient cost wise for the renter pilot is pedal to the metal. If it's a dry rental, different story.

What John said, just be careful if its wet rental with a tacho instead of a hobbs

@JohnK I tried "pedal to the metal" but cruising with full right rudder really made my cruise performance awful...

It depends on a lot of factors so it's hard to make generalizations. But for such a short flight, in most GA aircraft the minimum fuel burn profile is almost definitely flying the minimum legal altitude. Or the altitude with the most favorable winds, if there is a significant difference.
Here is a plot of the range profile of a Cessna 152 with standard tanks:

You can see that, at minimum cruise power, the range is maximum if flying at sea level and only decreases with higher altitude.
On the other hand, here is the same plot for a Cessna 152 with the optional extended range tanks:

You can see a modest increase in range up to 4000 feet and a decrease afterwards. The much longer flight allows for the modest efficiency gain of flying higher to make up for the extra fuel burned in the climb.
This is about a nine hour flight, though. It takes basically the whole 9 hours of fuel savings in cruise to make up for the fuel burned in the climb.
Note that these charts are based on a maximum performance climb. A somewhat faster airspeed climb could possibly give some fuel savings. But most POHs do not contain the information necessary to analyze fuel burn with arbitrary climb speeds.
This is based just off of fuel economy. Keep in mind that many maintenance costs depend on the number of hours spent in flight. Saving a few dollars on fuel isn't very helpful if it costs more than that in additional maintenance costs.

Few aircraft in the class of the 152 have a high enough service ceiling for reduced fuel burn at altitude to matter much, plus unless you have oxygen you're limited to 12,000 feet as a general rule.
Likely the biggest factor to save fuel with these aircraft is to avoid high throttle once you're clear of the airport and high enough to reduce throttle.  You'll burn a lot less per mile traveled at 70% than you would at 100% throttle, and reducing to 50% will save even more -- and because drag goes as the square of speed, flying, say, 20% slower saves more than 20% on fuel burn, so your overall "fuel mileage" is better when you throttle back.
Second is to ensure you're running the mixture as lean as EGT and head temperature (depending on available instruments) will allow.  Back in WWII, correct mixture management added more than 20% to the range of a P-38.

It took me a while to follow the logic of "the loss of speed is much less than the decrease in fuel burn" - is a clearer formulation of that sentence possible?  Perhaps just some emphasis that it's lower fuel per distance as well as per time.

Of course, the first person to use oxygen to set an altitude record did it by the simple expedient of shoving an oxygen tank under the seat and holding the end of the tube between his teeth... But eventually you'll also need extra air for the engine, so a supercharger may be in order...

Zeiss Ikon covers a lot of the points about operation of the physical aircraft but I think one of the most critical choices in light aircraft efficiency can be:
Winds Aloft
Your most economical flight path can be the one that takes the greatest advantage of winds aloft and/or avoids large headwinds. With modern flight planning apps like Foreflight you can generally see these options in realtime if you have programed your fuel burns in.
If you flying VFR you can take advantage (within safe altitudes) of choosing your cruse altitude to optimize tail winds and avoid head winds.
For example lets say I wanted to fly from KDXR to KDDH right now, I can climb up to 11,000 feet  where Im nice and high and close to my service ceiling but if i stay a bit lower at 5000 and take advantage of the tailwind Ill burn 2.9 less gallons of fuel and get there at the same time. Its worth noting this is my 55% lean mixture profile which is the most efficient for this aircraft. If time is of no factor to you this will generally always yield the lowest burns. The spreads are comparable at my other throttle positions with higher burns throughout.

(Source: Own Image)

Light aircrafts have special fuel consumption characteristics because of their design, dimensions, power plant and other factors. Small aircraft especially those used for private uses should have details on the performance factors among them being glide ratio and the climb rate. The recommended operating environment is at a height of 3,000 – 5,000 feet, and the most preferable climb and descent gradient should be a moderate gradient. More to do’s include the flight planning, management of the fuel and referring to the Pilot’s Operating Handbook (POH) for better performance.

Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center.

Although this answer is elegantly phrased, it doesn't actually answer the question.


text:
Am I allowed to take a liferaft onto a commerical flight?
I am planning on taking my aviation certified life-raft (Revere Aero Compact liferaft): "Raft inflates automatically in less than 30 seconds with self-contained CO₂ inflation system" on a commercial flight from Switzerland to Miami with Swiss. I have never travelled with it before, only when flying myself. Does anyone have any previous similar experience and is it even allowed in first place?

@TedS. - everyone wants to know!  Are you carrying this as a personal safety measure in case the aircraft ditches in the Atlantic, or, do you just need to transport it?

Hi I will be renting an airplane in florida to fly through the Caribbean ... I need it for ditching purposes, on the flight to the US it is used for the sake of transportation... Thanks

Ah!  Fascinating!  IDK the answer to your question - i guess it's a "call the airline" thing ...

I'd buy one from them
https://www.youtube.com/watch?v=B660im_JRjA
on the spot, very honest ("fishermen uses that, because they have to, but it can save lives, it is not really for an offshore [...]" )

"Should I take something onto a plane that will cause extreme alarm if it activates and which contains a small highly pressurised canister that could explode?"

@Richard Which works just like the life vests placed under your seat anyway.

Why should your life-raft be treated differently than any other item of luggage, please?
Is it banned outright?
Is it permitted as hold luggage but banned from the cabin - or vice-versa?
Is it permitted as any kind of luggage but prohibited by size or weight?

@user71659 - Yes, because a 30g CO2 cylinder is exactly the same as a 500g cylinder. No difference there at all

@RobbieGoodwin Sorry, my mistake. That was a response to Richard, not you. Two R names...

@user71659 Really? Then thanks, and I've deleted my Comment

@Richard That wasn't stated in your italicized text. Small highly pressurized cylinders are allowed. Large highly pressurized cylinders are required by law (emergency medical O2). Things like laptops and phones catch fire and cause emergency landings on a semi-regular basis. You cannot make a blanket assumption without diving into the specific dangerous goods regulation.

I decided to try and just put the life-raft inside my checked baggage today on a flight from Luxembourg to Zurich, as I arrived, it was still inside my bag, so I guess it worked out ... I will update this if it worked onto the flight to the US ;-) Thanks for the great help! Same goes for the flight back to Zurich.

Ted how was your flight?

@vasin1987 The flight was great, as expected with Swiss ;)

The CO2 cartridge will probably be considered as hazmat.  When I've traveled with Scouts with self-inflating life vests (going to a sailing camp), the vests all had to be in checked luggage.  Removing the CO2 cartridges would also work, but the easier solution for the Scouts was to have a dedicated checked bag with all the vests in it.  Don't know if removing the cartridge would be an option with your raft or not.
Best to check with the airline well in advance so you can make arrangements as necessary.

Thanks! That makes sense, I have previously travelled with a lifevest too, that wasnt too difficult either... So I guess they will be treated the same... Best Regards

If you don't mind putting it in checked luggage, then that is probably all you'll need.  Nevertheless, I'd check with the airline, as their rules may be different -- especially since they're under things beyond the FAA regs that I'm familiar with.

@TedS. The different is the size of the CO2 cylinder which will be much, much larger and will probably exceed the allowed limits.

Fascinating. I travel with a CO2 lifejacket regularly and have always been told specifically to carry it in hand luggage. The one time I had trouble with this, security insisted it had to go in the hold, I insisted the airline said it mustn't, until eventually I asked them what was under every seat on the plane. "Have a good flight, sir."

For life vests, IATA regulations say they can be brought on board as carry-on or checked luggage, but that you need operator approval, so individual airlines may have specific rules requiring one or the other. But life rafts (or rather the CO2 cartridge in there) are not allowed at all due to the size of the CO2 cylinder (unless it’s a teeny tiny raft I guess).

No. Life jackets and self-inflating devices are considered dangerous goods and can only be carried if registered in advance See Swiss Baggage rules.
I strongly suggest you contact the airline BEFORE you arrive at the airport. I would suggest you do it a number of days before as these things can take time.
This is not a Swiss specific regulation. All airlines have this restriction.

Note that the Swiss Baggage Rules mention "Life jacket or other self-inflating safety device intended to be worn by a person". Not sure how they will treat the life raft, but indeed, contacting the airline (and have quite some time to spend on that) is probably a good idea.

They have a hard limit of 50 ml on gas cartridges, but I can't find any info about the size of the cartridge on that life raft. Cartridges for similar life rafts I found clearly exceed that limit (by more than one order of magnitude).

Good point... I have not gotten any information by the company regarding the volume of C02...

Since the life raft is packed, and you are not allowed to unpack/repack it (only authorised service centres can do it), it will contain a full CO₂ cylinder.
IATA Dangerous Goods Regulations, and more specifically Provisions for Dangerous Goods Carried by Passengers or Crew have this to say:

Gas cartridges, small, non-flammable containing carbon dioxide or other suitable gas in Division 2.2. Up to two (2) small cartridges fitted into a self-inflating personal safety device, intended to be worn by a person, such as a life jacket or vest. Not more than two (2) devices per passenger and up to two (2) spare small cartridges per device, not more than four (4) cartridges up to 50 mL water capacity for other devices (see 2.3.4.2).

(emphasis theirs)
So there is no limit on the size of those CO₂ cylinders if they are fitted in a life vest or other personal safety device intended to be worn by a person (those are usually below 50 ml anyway).
For other devices such as your life raft, the limit is at 50 ml.
In both cases you can carry them in checked luggage or carry-on, but there is a limit of the number you can carry, and you need operator approval.
I wasn't able to find the size of the CO₂ cylinders in that life raft, but I've found cylinders for other rafts of similar size and they had a capacity of over 600 ml, so it seems very unlikely the CO₂ cylinder in your life raft will be small enough to be accepted. You may want to ask the manufacturer about the size of the cylinder, but I wouldn't hold my breath.
You'll need to ship your life raft separately (note that it must be correctly labeled as UN2990 class 9 dangerous goods).

If you are planning to carry a full CO2 cartridge: no.
From the TSA:

CO2 Cartridge Carry On Bags: No
Checked Bags: No
Except for personal
medical oxygen cylinders, you can only carry an EMPTY compressed gas
cylinder onboard a plane. To be permitted (in either carry-on or
checked baggage), it must be clearly visible to the TSA officer that
the cylinder is empty.

You looked up the wrong thing. See CO2 Cartidge for Life Vest, which is "Yes Special Instructions". Hazmat regulations may ban dangerous goods but allow them while contained in other items because the outer item protects the dangerous good. (Li-Ion batteries is the common example)

@user71659 no, because OP wants to bring a life raft, not a life vest. The former are allowed, the latter aren’t, due to the size of the CO2 cylinder.

It's due for inspection in 3 months anyway
So you might as well either leave the CO₂ cartridge in your home country ... or just drain/empty it and carry it separately.  Now you have no trouble with the carry-on.
Then, when you get to the USA, have a shop inspect and (as part of that) re-fill the CO₂ cartridge.
Now, you are sitting in Florida with a freshly inspected and freshly charged raft ready to go. Do your thing with it.
Now how do you get that home?  Easy - ground transportation. Take it to a Private Mail Box provider such as The UPS Store and they will cheerfully throw it in a box and mail it to your country.  Tell them it contains a charged CO₂ canister. If UPS/DHL/FedEx sticks it on an airplane improperly, not your problem.

It's quite possible it may actually not be a problem on a cargo plane, only a passenger plane (didn't check the Cargo DGR on this topic, only the Passenger one, they often have different rules, don't know if it's the case here).


text:
Why would my ADS-B airborne position decoding sometimes result in a latitude offset?
I am implementing my own ADS-B decoding station, mainly following Junzi Sun's work "The 1090 MegaHertz Riddle", and I am having an issue from time to time, with the latitude value having an offset of ±6 (which is quite a lot, enough to change country in my case), and I cannot find why this happens.
It can happen even if the correct airborne position has been decoded moments before, and/or moments after; and does not seem to be aircraft dependent. I am also doing the parity check, so the message received should be error proof.
I double checked my formulas, the NL check is done, all seems fine, and I cannot find the reason for this offset.
I am using an indoor installation for the moment, with a not too powerful antenna, as I am only in the testing phase, so I don't have a lot of range (less than 10km).  For the moment I have a maximum delay between frames of 60s (it will be put back to 10s later), because I don't receive lots of frames; could that be the issue? Note that the problem happens even if I reverse the order of even/odd frames. Also, I don't (yet) use locally unambiguous decoding, would it help?
Has someone experienced this before? Is there something I might be doing wrong? Should I just discard the values I know are false?

Does it happen at specific latitudes only?

When you use global decoding, do you make sure there is no more than  10 seconds betwee the odd and even messages?

I am using an indoor installation for the moment, with a not too powerful antenna, as I am only in the testing phase, so I don't have a lot of range (less than 10km). I will check if all the "lost" coordinates happen roughly at the same latitude (antenna is at approx lat 44-45).
For the moment I have a maximum delay between frames of 60s (it will be put back to 10s later), because I don't receive lots of frames, could that be the issue?
Note that the problem happens even if I reverse the order of even/odd frames.
Also, I don't (yet) use locally unanmbiguous decoding, would it help?

From a few data points, the latitude of the "wrong" decoded locations can vary by at least 10km (decoded lat is between 38.584 and 38.685). I should also point out that the offset value of 6 is an estimation, and it could very well be a non-integer offset, but that is a bit tricky to check

Do you mean a "sensitive antenna"?  Or are you transmitting?

Yes, I am not using a very sensitive antenna, and I am no transmitting

The jumps you see are caused by the fact that there is too much time between the two successive messages you use for the global unambiguous decoding.
For Compact Position Reporting (CPR) to work, the decoded positions of a global unambiguous decoding attempt should be no more than approximately 3 nautical miles apart. The standard (ED-102A / DO-260B) sets a limit of 10 seconds between reception of a pair of position reports for global unambiguous decoding. You will likely get away with 15 seconds in almost all cases.
However, in your case, you wait for up to 60 seconds. That is breaking the algorithm, and as a result you end up in the wrong latitude bin. You will likely see longitude errors as well.


text:
What is the maximum number of cabin crew members on an A320 load sheet?
What is the maximum allowable number of cabin crew members to be mentioned on the load sheet for A320, with respect to weight and balance? And does the number of deadheading crew members add to this figure ?

I believe that there are six crew seats in the A320 cabin. as long as the operating crew occupies these seats they will be included the crew figures for loadsheet purposes. In the event that these seats are occupied by non-crew they will need to be included manually. Not really common nowadays but it was routinely done in the 90s.
In the event that there is crew occupying a passenger seat (deadheading) they will be trimmed as a passenger.
The reason is most loadsheet programmes will adjust the Dry Operating Index  (and dry operating weight) depending on the number of crews entered in the crew field (eg 3/5). If a crew (deadheading or otherwise) is occupying a passenger seat, the system will only be able to account for this person if he is checked in.
Depending on the airline and the local country regulations it may not be possible for deadheading crews to travel on the General Declaration, instead they may be required to have tickets and be included in the passenger manifest.
To summarise, everything on the airplane must be accounted for, both in terms f weight as well as its effect on the trim, irrespective of whether it is a person on a jumpseat or passenger seat.
Hope this helps.

Thanks it really helps, but my point is it acceptable to add dead head crew to the active crew with a number above the available jump seat ?  Ex A 320 has 6 jump seats, is it possible for crew to be  2/10 ?

Hi Hossam, The various crew configurations available in the load-sheet system will only cater to the max number of crew seats available. You would only be able to select a combination from 2/0 to 4/6 (assuming only 6 crew seats available) as the technical services dept have only calculated the affect on the weight and trim in these seats.


text:
What kind of liquid can be seen 'leaking' from the upper surface of the wing of a Boeing 737-800?
Can anyone advise what the liquid seen on the wing of a 737-800 on approach as highlighted on the attached images is? The liquid was seen "pulsating" from the bases marked by the arrows. As the plane came to land, the intensity of the flow decreased until it eventually stopped altogether.

Lubricant, rain, melting ice.... Any liquid will vibrate when blasted with high winds.

Not exactly sure what you mean by Any liquid will vibrate when blasted with high winds. That liquid was throbbing from the edges that I marked so whatever this was, it came from within the wing so it's unlikely to be either ice. The conditions were dry and hot, so not conducing to ice formation.

You said it was pulsating. I meant the same by saying "vibrate." I simply meant that any liquid is going to pulsate/throb/vibrate in a strong wind. My guess would be it's lubricant but who knows? Small amounts of water can get inside a wing easily.

And leak out of the edges? The aircraft was in steady descent at a seemingly constant rate, and in smooth air.

@VH-NZZ the conditions were not dry and hot when the plane was at altitude. Even in hot weather, air at cruising altitudes is extremely cold.

@barbecue What makes you say that the aircraft was at "cruising altitude"? The pictures were taken at 2500-3000 ft AMSL, tops. OAT at sea level was 34 C. The lapse rate in standard atmosphere is 2 C/1000 ft. I can be satisfied that the area above my yellow arrows is condensation due to the cold fuel but what leaked in pulses was definitely not water.

@VH-NZZ The aircraft was previously at cruising altitude, which is when the fuel and wings became cold. 2C per thousand feet makes it around -30C to -40C at cruising altitudes.

the liquid is "water"

@VH-NZZ unless the aircraft spent the entire journey rolling down a highway, it was not in dry hot conditions throughout the journey. As I said, "the conditions were not dry and hot WHEN the plane was at altitude."

@VH-NZZ Unless you obtained a sample of the liquid and conducted chemical analysis, you can't claim it was not water.

The pictures show water condensation on the wing upper surface due to very cold fuel in main tank number 2.
The fuel is cold because the air temperature at cruise altitude is significantly colder than the air temperature encountered during the descent.
The condensation appears to be oozing from the wing but it is in fact flowing slowly over the surface, filling and overflowing every seam and imperfection.
Since you have provided photos and not a movie, I can't tell you what the "pulsating" really was, but it probably was either a slight boundary layer turbulence, or changes in the seam geometry due to wing flexing.

EDIT: There seems to be some confusion regarding the "pulsating" nature of the observed flow, with at least one correspondent1 insisting that the uneven flow proves that the fluid originates from inside the wing.
There are many mechanisms that could account for a pulsing or uneven flow of fluid over the wing, without resorting to the theory of a bleeding airplane.
The most likely reason depends on the fact that the wing surface is not a single sheet of metal, but contains discontinuous pieces such as spoilers, flaps, access panels, ailerons, etc. Because the wing flexes, the volumes of the spaces between these pieces, and the voids under some of them, continually change in flight.
Water flowing over the wing will fill some of these spaces and voids. Once a void is full, changes in volume will alternately squeeze out some water and suck some in. This could certainly look like a pulsating leak to someone who has not seen it before.
Another effect that can lead to pulsating does not require changing volume, but just a trough formed by the butting of two panels, roughly perpendicular to the airflow, filled by the trickling condensation. The air does not always flow smoothly over the wing2, and minor turbulence can press down on one section of the trough, causing water to spurt out of another section.
Seconds later the turbulent flow shifts, and the water hurries along the seam to pulsate in a different place.
The question can be completely resolved only by someone who can consider these theories while observing the effect.

The original poster, actually.
In spite of the large arrows painted on the wing surface.

I can be satisfied that the area above my yellow arrows is indeed condensation resulting from the cold fuel but what leaked in pulses was definitely not water or there would have been litres of it. It is unfortunate indeed that I did not take record a small movie.

@VH-NZZ There can be litres of water, why not?

@VH-NZZ A lot of air comes across an aircraft's wing in flight, and air can hold a lot of moisture. Have you done any back-of-the-envelope estimate of how much water could condense out of air on a cold wing of an aircraft at a given speed? Otherwise I have no idea why you would believe your intuition enough to say "it definitely wasn't water", given that our intuition evolved for scenarios that are completely different from what you're looking at here. Any number of things can result in pulsating behaviour; air is not homogenous. Heck, you usually get "pulses" of water in ordinary rain.

@VH-NZZ "Litres of water" are far from unexpected when flying at a low altitude over water. Evaporation fills the air with a lot of moisture and the wing surface after descending from cruise altitude is certainly way below the dew point of the ambient air. The wing surface comes in contact with dozens of cubic meters of air every second, with 10-20 grams of water in each cubic meter.

A contrail is the extreme example of condensation due to the passage of an aircraft (though not the exact mechanism as the one seen here). It's quite a large amount of water.

@VH-NZZ The only liquids it could plausibly be are fuel, hydraulic fluid and condensed water. Losing litres of either of the first two would be a huge problem; the fact that your plane didn't fall out of the air suggests quite strongly that it wasn't anything other than water.

the volumes of the spaces between these pieces, and the voids under some of them, continually change in flight, volumes that would be so impermeable as to retain water? Do you have any 737 wing schematic to back this assertion?

There's no need for a "schematic" to obviously see and know that any large mechanical object like a wing, motorcar, house, etc has innumerable gaps, separations, holes, small indentations etc. The pics just show condensation forming, drying off, forming, drying off. The pics just show just condensation run-off from the various bits and pieces you can see in the photo.

@Fattie A conjecture, at best, albeit not a very convincing one.

Since you have provided no film, no corroborating testimony, and no reaction from the airline operator, it must follow that conjecture is all the answer that anyone can ever provide. And as far as convincing is concerned, you don't seem to have convinced anyone that your airplane was leaking. - Frankly I am beginning to find your attitude a bit insulting.

authors: Vladimir F Героям слава


text:
What would be the effect of skinning over the gap in fixed leading-edge slats?
The Zenith STOL CH-750 experimental aircraft uses a modified NACA 650-18 airfoil (having a 17% fatter-than-normal thickness) with a fixed leading-edge slat.   In an effort to reduce drag and improve cruise performance, some of the builders remove the leading-edge slats.  Instead of removing the slats, I am curious what the effect would be if one left the slats in place, skinned over the slots with a removable leading edge (shown in red dotted line), and added vortex generators.

How would this modification affect the center of gravity for the aircraft?
Would this modification affect the chord length?
What are the pros and cons of such an experimental modification?

It would destroy the beneficial effect of the slats. The gap in the slats channels high pressure air from the bottom of the airfoil to the top of the airfoil, where it adds energy to the flow across the top of the airfoil, and increases the lift at any positive angle of attack. At low angle of attack (high speed), this would reduce form drag with negligible effect on lift, but at low speed (high AOA) it would increase induced drag significantly.

@Charles Bretana Yes, but that can be compensated with vortex generators.  There is an Italian-built clone of the Zenith 750 (the 'Savannah') that is supplied either with slats, or with no slats, but vortex generators in their place. I use to fly a Savannah with VGs, and it's close to impossible to stall (with some gas...).

I don't know about VGs, but maybe you meant to say, "could be replaced with VGs"? ... VGs, or no VGs, covering the gap in the slats destroys the effect of the slats...

@xxavier: If it is impossible to stall you don't have enough elevator authority. The vortex generators cannot prevent a stall and delay it only a bit.

@Peter Kämpf  It has lots of elevator authority. With the engine at 60%, you start pulling the stick, till the anemometer shows zero and the body of the plane gets vertical,  Or almost so...  With the engine at idle, a maximum of 45º is possible. Beyond that, a wing drops...

To answer your question, I suggest to look at the effect of slats. NACA technical report 407 studied a fixed slat similar to what is used on the Zenith CH-750, and the result of the optimum geometry is plotted below. Dashed lines are for the airfoil with a fixed slat and solid lines for the airfoil with the slot between slat and wing filled:

Lift and drag coefficients for a wing with and without a fixed slat over angle of attack, from NACA TR 407.
Three conclusions are obvious:

Drag is higher with a slat for no benefit in lift (even a small reduction, actually) up to an angle of attack of 15°. Don't let the scale of the plot mislead you: Zero-lift drag for the slotted wing was 0.0229 compared to 0.015 for the plain wing, an increase of 52.5%.
The maximum angle of attack has been increased by 9° by the slotted wing, from 15° to 24°. This translates into an increase in the maximum lift coefficient of 34.6% (from 1.297 to 1.751)
The stall behavior has changed from benign to outright nasty by the addition of the slot.

While the airfoil studied in NACA TR 407 is quite close, it is not exactly what happens once the slat is removed: While the outer contour of the airfoil did not change in NACA TR 407, those builders removed part of the wing when removing the slat. Therefore, wing area would be reduced and the loss in lift will actually be even greater. NACA TR 400 hints at a lift loss of more than 40%, which would increase the minimum speed of the Zenith CH-750 by about 30%. Note that the take-off and landing distances will grow accordingly - the STOL in the aircraft's name will not apply any longer!
When putting a glove over the slot, the wing area will be maintained and the minimum speed will not go up quite so severely. Using the 34.6% from NACA TR 407, the minimum speed increase would only be 23.6%. The change in airfoil shape (with the glove the point of maximum thickness is further back and the relative thickness smaller than with the slat removed) will not alter the flight characteristics in a significant way - in both cases the airfoil is of the peaky upper surface type with a large nose radius, so separation around stall will start from the trailing edge and move forward with increasing angle of attack. Long laminar runs on the top surface cannot be expected in both cases.
Now I only wonder why you would add vortex generators. I thought the idea was to reduce drag and improve cruise performance?

The idea IS to reduce drag and improve cruise performance...without sacrificing too much of the short field capabilities of the aircraft.  Per Vortex Generators: Band-Aids or Magic?,  an article in AVweb, by Mike Busch, "VGs do produce some drag, they also reduce drag by reducing the thickness of the boundary layer on the aft portion of the wing. The net result is about a "push" with no measurable degradation in cruise speed."  The article indicates that properly placed VGs result in low-speed performance improvements.  Best of both worlds, or Wishful thinking?

@MikeC. Wishful thinking. If they can give a "push", then only because the basic design was faulty. VGs can only reduce the boundary layer thickness if there was a separation before. A well designed airplane does not need them; they are a cheap and sometimes effective fix but no cure-all. In most cases, they raise drag for 95% of the time but do (sometimes) essential service in the last 5%. But they cannot do magic.

Why does that graph have two greatly-different curves for each of the two airfoils?

@Sean: Because one pair is for the lift coefficient ($c_L$) and the other for the drag coefficient ($c_D$). The round symbols are for the slotted version and the x and + symbols for the plain version.

@PeterKämpf: Ah, I see.  Thanx!